1. Field of the Invention
The present general inventive concept relates to an inkjet printhead, and more particularly, to a thermal inkjet printhead having a good print quality, a printing method using the same, and a method of manufacturing the inkjet printhead.
2. Description of the Related Art
In general, inkjet printers are devices used to form predetermined color images by ejecting minute ink droplets from an inkjet printhead to desired positions on a print medium. Inkjet printers are classified into a shuttle type inkjet printer whose inkjet printhead prints an image while reciprocating in a direction perpendicular to a print medium delivery direction, and a line printing type inkjet printer having a page-wide array printhead corresponding to a width of a print medium. The latter has recently been developed to achieve high-speed printing. The page-wide array printhead has a plurality of inkjet printheads arranged in a predetermined configuration. In the line printing type inkjet printer, during printing, the array printhead is fixed and only a print medium is transported, thereby enabling high-speed printing.
Inkjet printheds may be categorized into two types according to the ink droplet ejection mechanism thereof. The first one is a thermal inkjet printhead in which a heat source is used to generate and expand bubbles in ink, thereby ejecting ink droplets due to an expansion force of the bubbles. The other one is a piezoelectric inkjet printhead in which a piezoelectric body is deformed to exert pressure onto ink, thereby ejecting ink droplets.
An ink droplet ejection mechanism of a thermal inkjet printhead will now be explained in detail. When a pulse current is supplied to a heater including a heating resistor, the heater generates heat and ink near the heater is instantaneously heated up to approximately 300° C., thereby boiling the ink. Accordingly, ink bubbles are generated by ink evaporation, and the generated bubbles are expanded to exert pressure on the ink filled in an ink chamber. As a result, ink around a nozzle is ejected from the ink chamber in a form of droplets through the nozzle.
FIG. 1 is a cross-sectional view of a conventional thermal inkjet printhead. Referring to FIG. 1, the conventional thermal inkjet printhead includes a substrate 10 on which a plurality of material layers are formed, a chamber layer 20 stacked on the substrate 10, and a nozzle layer 30 stacked on the chamber layer 20. A plurality of ink chambers 22 filled with ink to be ejected are formed in the chamber layer 20. Nozzles 32 through which ink is ejected are formed in the nozzle layer 30. The substrate 10 has an ink feed hole 11 formed therethrough to supply ink to the ink chambers 22.
An insulating layer 12 is formed on a top surface of the substrate 10 to insulate the substrate 10 from a plurality of heaters 14. The plurality of heaters 14 are formed on a top surface of the insulating layer to heat the ink in the ink chambers 22 and generate bubbles. Electrodes 16 are formed on top surfaces of the heaters 14 to apply current to the heaters 14. A passivation layer 18 is formed on surfaces of the heaters 14 and the electrodes 16 to protect the heaters 14 and the electrodes 16. Anti-cavitation layers 19 are formed on the passivation layer 18 to protect the heaters 14 from a cavitation force generated when the bubbles collapse.
When there is a dead nozzle that leads to poor ink ejection, shuttle type inkjet printers can compensate for the dead nozzle since an inkjet printhead reciprocates from side to side, thereby preventing print quality degradation. However, line printing type inkjet printers including an array printhead wherein a plurality of inkjet printheads are arranged in a predetermined configuration are difficult to compensate for the dead nozzle since the array printhead is fixed during printing, thereby increasing the risk of impairing print quality.